Presuming the EMS agency you are interested in monitoring does tone and voice paging over VHF or UHF channels, you could conceivably do so. Motorola Minitor V pagers seem to be the most prevalent of the new ones.
I'm sure with some googling one could locate some pre-owned older models which may also suffice, however I'm skeptical about used equipment coming from an emergency service. As a guy with 39 years in the fire service, I know we ain't always "kind and gentle" to communications equipment.
You'd need to know the frequency used along with what specific tones to be used to activate the pager.
Owing to what frequencies are used by the agency, there's a remote chance that some of your Ham equipment could work too. If you have something that does Quick Call II signalling (at least that's what I think it's called), you could program it appropriately.
Many of the recent Uniden "top end" scanners do Fire Tone Out, which essentially makes these scanners "tone controlled paging receivers". So if you are going to plunk out $380+ for a pager, for a few bucks more you can have additional scanning potential.
